AVS 49th International Symposium
    Surface Science Tuesday Sessions
       Session SS1-TuM

Paper SS1-TuM9
In situ XPS Investigation of the Methanol Oxidation Over Copper

Tuesday, November 5, 2002, 11:00 am, Room C-108

Session: Hydrocarbon Catalysis
Presenter: H. Bluhm, Fritz Haber Institute of the Max Planck Society, Germany
Authors: H. Bluhm, Fritz Haber Institute of the Max Planck Society, Germany
M. Hävecker, Fritz Haber Institute of the Max Planck Society, Germany
A. Knop-Gericke, Fritz Haber Institute of the Max Planck Society, Germany
V.I. Bukhtiyarov, Boreskov Institute of Catalysis, Russia
D.F. Ogletree, Lawrence Berkeley National Laboratory
M. Salmeron, Lawrence Berkeley National Laboratory
R. Schlögl, Fritz Haber Institute of the Max Planck Society, Germany
Correspondent: Click to Email
We have used in situ X-ray photoelectron spectroscopy (XPS)@footnote 1@ in combination with mass spectrometry to investigate the partial oxidation of methanol to formaldehyde over a polycrystalline copper sample. The experiments were performed at a methanol to oxygen flow ratio of 3:1 (total pressure 0.4 torr) in the temperature range from 300 K to 750 K. The correlation of in-situ XPS spectra of the copper surface and the simultaneously obtained mass spectrometer data (which show the catalytic activity) allow us to draw conclusions about the electronic state of the catalyst under reaction conditions. Valence band and Oxygen 1s spectra show that after the onset of the catalytic reaction at T>550 K the copper surface has a metallic character. The Oxygen 1s spectra reveal that at least two different oxygen species with binding energies (BE) of 529.7 eV and 531.4 eV, respectively, are present at the catalytically active Cu surface. The O 1s peak at 529.7 eV is assigned to chemisorbed oxygen at the Cu surface. The integrated intensity of the chemisorbed oxygen peak is proportional to the amount of formaldehyde that is produced in the catalytic reaction. The peak at 531.4 eV is assigned to subsurface oxygen. The formaldehyde yield increases linearly with the integrated intensity of the subsurface oxygen peak, up to a concentration of the equivalent of about one monolayer of subsurface oxygen. A further increase of the amount of subsurface oxygen does not lead to an increase of the formaldehyde yield. @FootnoteText@ @footnote 1@ D.F. Ogletree, H. Bluhm, G. Lebedev, C.S. Fadley, Z. Hussain, M. Salmeron, submitted to Rev. Sci. Instrum.